He was educated at Trinity College, Dublin, entering on 22 November 1755, and taking a B.A.
[2] Ledwich died at his house in York Street, Dublin, on 8 August 1823.
It was later discounted, because of the imperfect information on Irish history current in his day, and his theories were effectually set aside by George Petrie and later writers.
In the index to John Lanigan's Ecclesiastical History there are errata to Ledwich.
[2] In 1791, Ledwich completed the editing and publication of his friend Francis Grose's Antiquities of Ireland.